The high-speed rail link was once the locomotive embodiment of the ideal of a border-free Continent. But Britain's withdrawal from the EU leaves the service facing an uncertain future.
Just as the high-speed train dived under the English Channel, Mujtaba Rahman frantically typed an email on his smartphone and hit send.
A short ride later, through a dark void that briefly blocked both his ears and his cellphone reception, he was hurtling across the rolling fields of France. "On the way in and out of the tunnel is a really good time to do some thinking," Rahman said.
What he thinks a lot about these days is Brexit. Rahman once worked for the British government, helping tie its fortunes ever more closely to the European Union. Today, he consults private clients on the risks of Britain's withdrawal from the bloc.
He is part of a tribe of lawyers, economists, journalists and trade experts who helped turn the high-speed train, known as the Eurostar, into the embodiment of the idea of the near-borderless world that the EU stood for.
Ironically, the Eurostar, which turned 25 last week, has become the primary vehicle they use for going back and forth to undo the relationship they once helped build.
For those living in London, the Eurostar has made weekends in Paris (or Brussels, or now even Amsterdam) — or vice versa — simple, fast and relatively affordable. It enabled a professional class to bounce back and forth under the English Channel that once served as a moat — protective or isolating, depending on the traveller's perspective.
These days, regular passengers include the British negotiators working on pulling their country out of the EU, who have often boarded the train twice a week to head to Brussels for talks about the divorce.
And then there are the others, like Rahman, whose professional lives revolve around the links that are being severed.
If Brexit eventually happens, as seems likely, the ease of travel they have depended on, contingent on quick immigration checks for EU passport holders, seems certain to change.
The fate of the train itself may hang in the balance. For now, the executives who run it watch and wait.
Tickets are still selling fast. In August, a record total of 1 million passengers rode the Eurostar between London and its destinations of Paris, Brussels and Amsterdam. The company reported booming profits in 2017 and 2018, and has strengthened its marketing, bolstered by American demand and a growing preference for green travel.
But the Eurostar's future will depend a lot on what Brexit ultimately looks like. A no-deal withdrawal could be catastrophic for business.
Documents leaked to the news media this year predicted that a no-deal or "hard" Brexit precipitating stricter and time-consuming passport checks by French authorities would prompt 15,000-people-long lines at St. Pancras, the major rail station in London served by the Eurostar.
Officials and experts predict privately that the company would not survive more than 12 weeks in such an adverse scenario.
Eurostar said that the doomsday scenario was "misleading."
"We have worked closely with governments on both sides of the Channel, including the Department for Transport, to ensure that we continue operating in a deal or no-deal scenario," Rosie Jones, a spokeswoman, said in an email.
"Eurostar has been working extensively with our station partners, governments and control authorities on both sides of the Channel to ensure that robust plans are in place to protect services and to manage customer flows effectively," she added.
For now, the Eurostar shoots back and forth every day, beneath the Channel, catapulting its traveling tribe between the European capitals. Private and professional lives have been formed and played out through this linkup, and careers will continue to be built around it in a post-Brexit world.
Rahman's entire adult life is a case in point. A Briton by birth, he quickly became drawn to EU policymaking and specialized in the subject at university.
He joined the British Civil Service as an entry-level professional in a special program that fast-tracks promising graduates with expertise in the EU.
Having spent three years in Brussels on secondment from the British government, Rahman jumped to the private sector, where he is a prominent analyst, heading up the Europe practice at Eurasia Group, a political-risk consulting firm.
He says the seeds of Brexit were sown from the start of Britain's relationship with Europe.
"Britain always sought to extract economic benefits of being a member of the club, without any of the political consequences of being one," Rahman said. "It sought to retain sovereignty to the greatest extent possible, it never signed up to political integration."
Rahman likes the time he spends on the train, he said on a recent trip as the high-speed shuttle entered the so-called Eurotunnel, the undersea passage that links Britain to France, an engineering feat and the world's longest underwater railway corridor.
Nina dos Santos, Europe editor for CNN, said she remembered being a student at a French school in London when the Eurotunnel was inaugurated in 1994; some of her schoolmates were the children of French engineers working on the groundbreaking piece of infrastructure.
Today, she regularly rides back and forth between London, where she's based at the American network's Europe headquarters, and Brussels, where she goes to cover Brexit.
"I've been riding this train to Brussels for 15 years," she said sipping coffee on a recent morning across the street from the European Commission building in Brussels. Dos Santos, who speaks six languages, said she sometimes overheard other passengers' conversations on the Eurostar.
"So many people are in similar lines of business — lobbying the EU, lawyers, politicians and so on — and so often it's like a little bubble of us traveling between the two cities, a microcosm of Britain's EU membership," she said.
Many of those who once took this train from Brussels to advise companies in London on how to influence the EU's industry regulations now travel to advise them on how to survive the withdrawal and navigate the post-Brexit world.
Sebastian Vos is one of them. Born in The Hague, Vos is a top lobbyist in Brussels, heading up the policy practice for Europe at Covington, a US law firm.
He predicted that many of his clients, among them some major technology firms, would not abandon London and, regardless of the changes, would continue to be hugely affected by EU policies.
When Britain leaves the EU (or "if," as Vos likes to stress), part of his job will be to advise his clients on how to continue complying with regulations in Europe and in Britain, and how to tackle the possibility that some of those regulations will diverge, as London begins to carve out its own rules.
"Brexit, if it does happen, will definitely lead to all kinds of friction," Vos said, though he added that the original shock of the withdrawal had waned.
Georgina Wright, a senior researcher at the London-based Institute of Government think tank, said that the one thing that could not happen was that Britain cut itself off fully from the Continent.
"You can't unplug the UK from the EU — energy, data flows, there are all these pipelines that run between the two," she noted.
The Eurostar, she says, is one of those links, and one that has had a special role in her own life.
Born to British parents and raised in Brussels, Wright said she remembered what a game changer it was when the Eurotunnel was built and introduced a shuttle for passengers who wanted to take their cars to Britain from mainland Europe.
Before that, Wright said, when the family went on their regular visits to grandparents in England, they would wake up early, drive to Calais, France, and wait in the bitter cold to board a ferry that would take them, slowly, to Dover, England.
Even with Brexit pending, some are starting to look to the future and what Britain's new relationship with the European Union will look like.
Rahman predicts a flurry of activity, with British officials riding the train to Brussels regularly to negotiate the new, post-divorce links.
Wright agreed. "If you think the Brexit negotiations have been complicated, wait until we start negotiating the future," she said with a chuckle.
Written by: Matina Stevis-Gridneff
Photographs by: Mary Turner
© 2019 THE NEW YORK TIMES